Electronic Power System board – contains the control electronics and the TTC node used for communication with the OBDH via CITATION OBD \l 2057 (OBDH – PSU Interface)

TTC Node: Used for measuring the state of the system, needs to relate data to the OBDH unit. Made up of a microcontroller, ADC, flash memory and interface. It senses different parameters of the PSU system, then converts this to digital data via the ADC. eg solar panel temperature, battery voltage etc.

Battery heater: can be an independent temperature sensing unit.

Electrical interface design – ensure that the rise and fall times of the digital signals fall within reasonable limits, along with current and voltage limiting.

ESD – Electrostatic Discharge. Ensure that the components are protected from electrostatic discharge throughout mission life, including in construction. NOTE – When handling all components, need anti-static conditions, and gloves to avoid corrosion due to organic materials.

Majority of testing of power circuitry through a solar array simulation (power supply with similar characteristics to that of a solar array) and payload simulations (try and match loads that will be required in operation).

Batteries likely to be bought from clydespace, data sheet of potential batteries can be seen in power examples folder. Talking to Clydespace can give us a better idea of what batteries we will finally choose. For the pursposes of simulating the operation of the cubesat, we do not need the batteries at the early stages, only for late-stage integration after battery testing and the power system has been tested in isolation with a power supply.
EPS

The electronic power supply unit comprises of many subsystems, that together control and co-ordinate the power delivery for the cubesat subsystems.

BCR

Battery charge regulators ensure that the battery is safely and efficiently charged over its lifecycle. Withought sufficient regulation, the batteries will have a shorter life, and in the case of Li-Po batteries (the most likely to be used in this mission) they will explode. These have to be designed to suit the particular type of solar array used. These automatically match the solar panel voltage to that of their input in order to maximise power transfer. This is required because of the variable voltages that will be generated with different levels of irradiance incident on the panels of the cubesat.

TLM/TTC

There is an onboard microcontroller that is I2C compatible (I2C compatibility will be an area that needs to be taken on board by an team when integrating the electronics). In the Clydespace board being analysed, they do not go into detail about how the telemetry is achieved. The team investigating the EPS will have to look further into different ways of measuring voltages, currents temperature etc. of an electronic system, and converting this into readable data. Most likely, the TTC unit consists of a microcontroller, with memory for datalogging, and an ADC to read the voltages and currents. The microcontroller(s) will have several tasks. To convert and store the signal in the data logging unit, ready for readings to be sent through downlink and to activate circuit protection if any of the values exceed the predetermined limits. A level of autonomy (and possibly reprogrammability) will have to be built into the TTC node.

PCU

Basically just a DC/DC step down voltage regulator, or array of them. On the Clydespace board, they use large toroidal inductors, which could be replaced with more modern flatter ones, (I used a very compact 3A inductor on my voltage regulator for the legged walking robot, which would be smaller lighter and probably more efficient. This is an example of why we should look at producing our own subsystems – there is potential for improvement upon the Clydespace design. And if it wouldn’t be an improvement, just an obnoxious failure, then there is that potential for learning!) These will provide different voltages, such as 5V or 3.3V for various components to be used in the design.

Protection

Circuits in place to break the circuit if there is a short, or sense any over-current or over voltages occurring. Time-dependent, resettable fuse type designs could be useful here.

Power Production

This requires calculations depending on the best and worst case scenarios for the cubesat. An example of this could be the hexagonal area when the cube has a corner pointing directly towards the sun, thus presenting a hexagonal surface area. The surface area where light would be incident on the solar panels would be at a minimum when a singular square face of the cubesat is pointing the sun. These calculations would be key to the power budget, and one of the very first design steps will be to calculate the maximum available power.
Interfacing

The different parts of the system will need to communicate, and appropriate interfacing will have to be developed. This will require a knowledge of all subsystems, the microcontroller, the bus pins to be used and the use of I2C infrastructure.